Impact/Purpose:

This paper reports the results of in vitro and in vivo bioassays which indicate relatively high levels of estrogenicity (relative to reports on a number of other U.S. surface waters) in waters of the South Platte River in Colorado in proximity to wastewater treatment plant outfalls. The work informs efforts by Region 8 to estimate and understand potential impacts of anthropogenic contaminants, including endocrine active chemicals, on ecosystem services provided by the South Platte as a major freshwater resource along the Colorado Front Range and Eastern Plains. Comparing the intensities of these responses to earlier reports by other researchers suggest that resident biota may be at risk for adverse reproductive effects at these sites. We recommend further investigations particularly with regard to assessing the benefits of recent upgrades in wastewater treatment technologies. The case study also demonstrates the application of novel pathway-based environmental surveillance and monitoring approaches under development as part of the Adverse Outcome Pathway Discovery and Development project (CSS 17.01) currently conducted under the Chemical Safety for Sustainability National Program.

Description:

Rivers in the arid Western United States face increasing influences from anthropogenic contaminants due to population growth, urbanization, and drought. To better understand and more effectively track the impacts of these contaminants, biologically-based monitoring tools are increasingly being used to complement routine chemical monitoring. This study was initiated to assess the ability of both targeted and untargeted biologically-based monitoring tools to discriminate impacts of two adjacent wastewater treatment plants (WWTPs) on Colorado's South Platte River. A cell-based estrogen assay (in vitro, targeted) determined that water samples collected downstream of the larger of the two WWTPs displayed considerable estrogenic activity in its two separate effluent streams. Hepatic vitellogenin mRNA expression (in vivo, targeted) and NMR-based metabolomic analyses (in vivo, untargeted) from caged male fathead minnows also suggested estrogenic activity downstream of the larger WWTP, but detected significant differences in responses from its two effluent streams. The metabolomic results suggested that these differences were associated with oxidative stress levels. Finally, partial least squares regression was used to explore linkages between the metabolomics responses and the chemical contaminants that were detected at the sites. This analysis, along with univariate statistical approaches, identified significant covariance between the biological endpoints and estrone concentrations, suggesting the importance of this contaminant and recommending increased focus on its presence in the environment. These results underscore the benefits of a combined targeted and untargeted biologically-based monitoring strategy when used alongside contaminant monitoring to more effectively assess ecological impacts of exposures to complex mixtures in surface waters.